Question: 4 binders cost $4.96. Which equation would help determine the cost of 9 binders?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 4 binders cost $4.96 as a proportion: $\dfrac{4}{\$4.96}$ Let $x$ represent the unknown cost of 9 binders. Since 9 binders cost $x$ , we have the following proportion: $\dfrac{9}{x}$ The cost changes along with the number of binders purchased, and so the two proportions are equivalent. $\dfrac{4}{\$4.96} = \dfrac{9}{x}$